The present invention is directed to hog type granulating machines for the size reduction of heavy plastic parts. Devices of this general type are in common application through out the plastics industry but include a number of operational drawbacks which the novel present machine overcomes. One such operational drawback of prior art devices are their generally high power requirements. Efforts to reduce the power requirements of such machines have resulted in machines exhibiting a tendency to stall under heavy load. Accordingly, a desirable feature and object of the present invention is the use of rotor knives having spaced blade portions which are laterally offset from each other which in combination with other features as will be hereinafter more apparent combine to produce a device having low power consumption but yet one which avoids the stalling tendencies of the prior art devices.
Known constructions of rotor knife blades further exhibit a tendency to require periodic regrinding of their cutting edges to maintain sharpness. In many prior art devices such regrinding reduces the projecting portion of the rotor blade to either render the blades useless or require shims or other adjustment means to increase their outward extension so as to project outwardly from the rotor in a cutting pattern. Accordingly, a further object of the present invention is a blade construction configured so as to reduce the necessity of its readjustment relative to its supporting rotor portions and further provides a blade having a geometric configuration such that material passing thereacross hones an upper trailing edge of the blade so as to continuously provide a sharpening action upon the blade so as to greatly increase the amount of plastic material which can be granulated before the blade must be reground.
Still another object of the present invention is the provision of rotor knives so configured so as to eliminate hard to clean pockets or undercut portions in which material cut may be entrapped during cutting so as to reduce the cleaning down time of such machines and accordingly enhance their output.
Still another object of the invention is the provision of means to reduce the tendency of chunks of material being granulated from riding on top of the rotor and from being frequently thrown upwardly inside the chamber of the machine as is common in prior art devices so as to better enable the granulation of such smaller chunks of material, thus assuring more complete and more rapid granulation.
These and other objects of the invention that will become apparent in the foregoing description are accomplished by the provision of a granulator comprising a chamber, a generally cylindrical rotor mounted within a chamber for rotation about an axis, means for driving the rotor about the axis, cutting means comprising a plurality of knives affixed to the rotor and situated in cutting relation with bed knives as the rotor is driven to effect reduction of material fed into the chamber. The rotor is provided with a plurality of partially cutout portions forming the seats for individual rotor knives having a plurality of outwardly extending spaced blade portions which may be mounted in combination with continuous knives alternating therewith and wherein the downstroke portions of such chamber is provided with a material backup portion or support either of a continuous surface or having a plurality of vertically orientated slots. The support sections serve to force plastic material to be cut, to be shifted arcuately higher on the rotor so that the impact of the blades contacts such material in a more horizontal direction than in prior art devices. The plurality of spaced vertical slots reduces the tendency for partially granulated material to bounce within the chamber.
The granulating machine of the present invention is further provided with particular cutting blade geometry having a trailing edge and exhibiting a hook-shaped face portion including a downwardly inwardly directed face edge which serves to provide a pocket for partially severed material and which further enables the drawing of material being cut across said trailing edge so as to longer maintain an effective cutting edge on the blade.
Other objects and features of the invention become more apparent by reference to the following drawings and detailed description of the invention.